1. Field of the Invention
This invention relates generally to power supplies and, more particularly, to a start-up circuit for supplying energy to a user circuit.
2. Description of the Prior Art
Known start-up circuits generally require the use of large step down or filament type transformers or, in the alternative, series pass transistor circuits which perform voltage step down from the AC line voltage. Both are costly and add to the overall complexity of the circuit. Furthermore, the use of low voltage transformers adds significantly to the weight of the circuit. Since the filtered AC line voltage is nominally 325 volts and may reach as high as 400 volts, the step down transistor circuit may suffer severe overheating since the user circuit may require logic level voltages (e.g. less than 10 volts).